In a magnetic storage apparatus (which is generally known as a magnetic recording apparatus) such as a magnetic disk apparatus or a magneto-optical disk apparatus used as an external storage device for a computer, a data read operation is performed by recording magnetic information in a designated position (for example, a designated track) on the magnetic recording surface of a magnetic recording medium, such as a disk by using a magnetic head-exemplified by a thin-film magnetic head, and a data read operation is performed by reproducing (reading) information recorded in a designated position on the magnetic recording surface.
In the field of such a magnetic recording device, the need for larger recording capacity and higher recording density has been increasing more than ever before. To achieve higher recording density, the size of the crystal grains contained in the magnetic recording layer of magnetic recording media must be made even smaller and more uniform. The reason is that if relatively large crystal grains remain, magnetic reversals may not be fully accomplished for all the crystal grains when writing data, and in some regions, the direction of magnetization may remain unreversed. The presence of such unreversed regions can result in noise when writing data. There is therefore a need to make the crystal grains as fine as possible in order to reduce the occurrence of such regions.
In the case of longitudinal magnetic recording in which the direction of magnetization in the magnetic recording layer is parallel to the plane of the magnetic recording medium, the recording density has already reached its limit due to thermal stability, and therefore, vertical magnetic recording in which the direction of magnetization in the magnetic recording layer is perpendicular to the plane of the magnetic recording medium is becoming the predominant method. In the next generation of magnetic recording media employing the vertical magnetic recording technology, it will be necessary for even higher recording density, but to satisfy such a need, a high magnetic anisotropy material having a high magnetic anisotropy energy has to be used.
However, the theoretical limit of the maximum value of the magnetic field that can be generated by a magnetic head is about 16 kOe (1273 kA/m (amperes/meter) in SI unit system). Therefore, in the future, a situation may occur where data cannot be written to a magnetic recording medium fabricated using a high magnetic anisotropy material. In other words, it may be difficult for vertical magnetic recording technology to satisfy the need to further increase the recording density of magnetic recording media. To address this problem, a technology is needed that reduces the magnetic anisotropy energy of the high magnetic anisotropy material only when writing data, so that data can be written stably to a magnetic recording medium fabricated using a high magnetic anisotropy material, while allowing the use of a conventional magnetic head.
For reference purposes, patent documents 1 and 2 are presented below as prior art documents disclosing magnetic head structures relating to conventional vertical magnetic recording technology.
However, patent documents 1 and 2 only disclose the structures of magnetic heads for writing data to vertical magnetic recording media, and neither makes any mention of the structure of the vertical magnetic recording medium itself.    Patent document 1: Japanese Unexamined Patent Publication No. S59-019220    Patent document 2: Japanese Unexamined Patent Publication No. S58-068209